The Nuremberg Code is not really relevant to modern medical ethics, or even to the history of medical ethics--its authors plagiarized [1] half of it from the 1931 Guidelines for Human Experimentation [2]. The relevant standard these days is the seventh revision of the Declaration of Helsinki, by the World Medical Association.
No, the use of COVID-19 vaccines was not "experimental" [3]:
> COVID-19 vaccines used in practice and involved in vaccination mandates are either authorized or fully approved by national regulatory authorities. Hence, they are not experimental and not part of research, and thus not covered by the Nuremberg Code. Taking approved medicines prescribed or used as a matter of regular medical or public health practice does not constitute an experiment or research in any common understandings of the terms.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3121268/
[2] https://en.wikipedia.org/wiki/Guidelines_for_human_subject_r...